Process for removing shale from a naturally occurring borate



Patented Apr. 25, 1939 PROCESS FOR. REMOVING SHALEV FROM A? I J NATURALLY OQCURRING BORATE.

Geor-ge A. Connell, San Pedro, andJolin Boron, Calif., assignorsto Pacific Coast Borax Company, a corporation of Nevada No Drawing. ApplicationLMayj9.51938 1? Serial-No. 206,846

3 Claims.- (01. 20956) This invention relates to the removal of insoluble impurities from'naturally occurring borates in suflicient degree to give a merchantable product.

' r, Most boratedeposits are believed to have been formed by the drying up of lakes, the waters of which contain borates, or by the deposition of sodium or calcium borate in old sedimentary shale beds. These borates generally are sodium tetraborate decahydrate, sodium tetraborate tetrahydrate, calcium sodium borate such as ulexite, or calcium borate such as colemanite. In the deposition of these various borates fine mud is generally included with the crystals. This mud,

under the conditions associated with the deposit, becomes hardened into the form of shale. 'The result is that practically all the deposits are not deposits of pure borates but have associated with the borates considerable insoluble impurities in the form of shale. This shale may be calcareous or agrillacious and is generally rather hard.

Due to the presence of these insoluble impurities, generally in the form of shale, borates as mined cannot be used without purification of some sort. Usually this is done by dissolving the borate, if it is a sodium borate or decomposing with sodium carbonate if calcium borate and filtering out the mud and then crystallizing the sodium borate. Other means of improving the borate are in use but all methods are rather expensive. It has been thought that if the shale impurities could be softened by water so as to form a slime this slime could be separated from the coarser borate crystals by hindered settling, screening or decantation. However, it has been found that the shale occurring along with the borates is generally bound together with small amounts of the borates and that this shale ordinarily will not slime when soaked Without dissolving such amounts of the borates as to preclude such practice as a commercial operation.

It is an object of our invention to produce a simple and efficient method or process whereby the shales and other earthy matter occurring in borate ores may be readily separated and removed from the ore in such a manner that commercially pure borate may be produced at low cost and expense.

We have discovered that if a mixture of natural occurring borate, such as tincal, ulexite, colemanite or the like, and the shale be exposed to a rubbing action in a cylinder containing rubber covered balls or rods with a satu rated solution of the borates, then a large majority. of thei shale and earthy material present is slime'd and easily. rem0vedfrom the larger sized-borate crystals.- I

. in carrying out the methodiherein disclosed the ore .is vfinely crushed to approximately eight 5 or nine mesh. The crushing operation results in a mixture of particles of borate and particles of shale combined with earthy matter cemented or bound together by borate material. This mixed material is then introduced into a saturated solu- 10 tion of borate. Such solution softens the shale and earthy material so that upon agitation the particles of shale and earth matter disintegrate. This action is accelerated if the agitation is performed in the presence of a yieldable surfaced 15 container or in a container having movable yieldable surfaced units such as above referred to.

After the step of agitation just described the resultant pulp is screened over a two hundred mesh screen and the oversize material air dried. 20 With this method the oversize material consists largely of borate crystals as appears from the following examples.

It is to be understood that instead of screening that other methods of final separation may 25 be utilized such as hydraulic classifying.

As an example, 244 grams of a tincal ore were agitated in a two quart reagent bottle half filled with rubber balls along with 250 cc. of saturated tincal solution for ten minutes. The resulting 30 pulp was then screened over a 200 mesh screen and the material on the 200 mesh screen was air dried and analyzed.

Analysis of Analysis of material after orlgmal ore sliming and screening Percent Percent 40 Tmcal 59. 5 95. 2 Water insoluble 40. 0 4. 2

500 cc. of saturated borate solution for fifteen minutes.

Analysis of Analysis after original ore concentrating Percent Percent Calcium borates 67 Water insolubles 33 2 This concentration was accomplished by recovering 98%v of the original borate mineral and making a relatively pure-calcium borate product.

The above outlined method provides a satisfactory commercially feasible way of separating We claim as our invention:

1. The method of recovering borate from its ore which includes, finely crushing the ore, introducing the crushed ore into saturated solution of the borate, agitating the mixture in the presence of yieldable surfaced attrition members, and separating the solid borates from the slimes resultant from. the mixture.

2. The method of recovering borate from its ore which consists in, grinding the ore to approximately 9 mesh, mixing the ground ore with asaturated solution of the borate, agitating the mixture in the presence of yieldable surfaced attrition members and screening the resultant mixture to separate the particles of borate from the mixture.

3. The method of recovering borate from its ore which consists in crushing the ore, forming a saturated solution of the ore, mixing the crushed ore with the saturated solution, agitating the mixture and separating the borate crystals from. the resultant slimes.

GEORGE A. CONNELL. JOHN P. RASOR. 

